Catalyst demetallization effluent treating



Sept. 22, 1964 K. A- SMITH ETAL Filed Nov. 28. 1960 aMOl DIV/H917 3.95

CATALYST DEMETALLIZATION EFFLUENT TREATING 201 UB'BNEQJH I l l I IINVENTIORS KENNETH A. SMITH WILLIAM B. WATSON BY @VQ/Kaw/w/m/ f Ma,

ATTORNEY United States Patent Oil ice 3,150,074 Patented Sept. 22, 19643,150,074 CATALYST BEMETALLHZATION EFFLUENT TREATING Kenneth A. Smith,Homewood, and William B. Watson,

Park Forest, lll., assignors, by mesne assignments, to

Sinclair Research, inc., New York, NPY., a corporation of Delaware FiledNov. 28, 1960, Ser. No. 72,053 i3 Claims. (Cl. 208-113) This inventionis a method for producing and treating gasoline which employs catalyticcracking of a feedstock containing metal contaminants, demetallizationof the catalyst and destruction of poisonous materials andneutralization of waste materials from the demetallization by wastematerials from the gasoline treatment.

Catalytically promoted methods for the chemical conversion ofhydrocarbons include cracking of heavier hydrocarbon feedstocks toproduce hydrocarbons of preferred octane rating boiling in the gasolinerange. Feedstocks to these processes comprise normally liquid and solidhydrocarbons which are fed, usually in the fluid, i.e. liquid or vapor,state to one of a variety of solid oxide catalysts generally attemperatures of about 750 to l100 F., preferably about 850 to 950 F., atpressures up to about 2000 psig., preferably about atmospheric to 100p.s.i.g., and without substantial addition of free hydrogen to thesystem. In cracking, the feedstock is usually a mineral oil or petroleumhydrocarbon fraction such as straight run or recycle gas oils or othernormally liquid hydrocarbons boiling above the gasoline range.

Petroleum reiiners try to avoid the use of cracking feedstocks which areknown to contain significant amounts of metals since most of thesemetals, when presen-t in a stock, either naturally or through Contactwith metallic apparatus, deposit as a non-volatile compound on thecatalyst during the conversion processes so that regeneration of thecatalyst to remove coke does not remove these contaminants. lt is to beunderstood that the term metal used herein refers to both elementalmetals and metal compounds. In particular, iron, nickel, vanadium andcopper from a feedstock deposit on the catalyst markedly altering theselectivity and activity oi cracking reactions, generally producing ahigher yield of coke and hydrogen at the expense of desired products,such as gasoline, butylenes and butanes. For instance, it has been shownthat the yield of butanes, butylenes and gasoline, based on converting60 volume percent of cracking feed to lighter materials and coke,dropped from 58.5 to 49.6 volume percent when the amount of nickel onthe catalyst increased from 55 ppm. to 645 ppm. and the amount ofvanadium from 145 ppm. to 1480 p.p.m. in iluid catalytic cracking of afeedstock containing some metal contaminated marginal stocks.

Rather than permit metals levels on the catalyst to increase when apoisonous feed must be used, many refiners merely replace contaminatedcatalyst frequently with virgin unpoisoned catalyst. However, it hasbeen found possible to employ specialized techniques to remove metalcontaminants from a poisoned cracking catalyst. It has been found, forexample, that a catalyst which has been contaminated with Fe, Ni and/orV by use in the high temperature conversion of feedstocks containingthese metals may be demetallized by chlorination treatment followed byan acidic aqueous wash. This invention uses such demctallizationtechniques and also disposes of the waste acid gases and liquids fromthe demetallization by exploiting the acid values.

Solid oxide catalyst have long been recognized as useful incatalytically promoting conversion of hydrocarbons. For crackingprocesses, the catalysts which have received the widest acceptance todayare usually activ-ated or calcined predominantly silica or silica-based,e.g. silica-alumina, silica-magnesia or silica-zirconia, etc.,compositions in a state of very slight hydration and containing smallamounts of acidic oxide promoters in many instances. The oxide catalystmay be aluminaor silicabased and ordinarily contains a substantialamount of a gel or gelatinous precipitate comprising a major portion ofsilica and at least one other material, such as alumina, rnagnesia,zirconia, etc. These oxides may also contain small amounts of otherinorganic materials, but current practice in catalytic cracking leansmore toward the exclusion from the silica hydrate materials of foreignconstituents such as alkaline salts which may cause sintering of thecatalyst surface on regeneration and a drop in catalytic activity. Forthis reason, the use of wholly or partially synthetic gel catalysts,which are more uniform and less damaged by high temperatures intreatment and regeneration, is often preferable. Popular synthetic gelcracking catalysts generally contain about 10 to 30% alumina on silica.Two such catalysts are Aerocat which contains about 13% A1203, and HighAlumina Nalcat which contains about 25% A1203, with substantially thebalance being silica. The catalyst may be only partially of syntheticmaterial; for example, it may be made by the precipitation ofsilica-alumina on an activated clay, such as kao-linite or halloysite.One such semi-synthetic catalyst contains about equal amounts ofsilica-alumina gel and clay. Such commercially used cracking catalystsare the result of years of study and research into the nature ofcracking catalysis, and the cost or" these catalysts is not negligible.The expense of such catalysts, however, is justitied because thecomposition, s-tructure, porosity and other characteristics of suchcatalysts are rigidly controlled so that they may give optimum resultsin cracking. it is important therefore, that removing poisoning metalsfrom the catalyst does not jeopardize the desired chemical and physicalconstitution of the catalyst. Although methods have been suggested inthe past for removing poisoning metals from a catalyst which has beenused for high-temperature hydrocarbon conversions, for example, theprocesses of US. Patents 2,488,718; 2,488,744; 2,668,798 and 2,693,-455; the processes used herein are effective to remove metals withoutendangering the expensive catalyst.

ln this invention, the hydrocarbon petroleum oils utilized as feedstockfor a conversion process may be of any desired type normally utilized incatalytic conversion operations, and will generally contain metalcontaminants, sometimes as much as 3%. The feedstock generally boilsprimarily in the gas-oil range or higher, that is, from about 400 to1400 F. The catalyst may be used as a iixed, moving or fluidized bed ormay be in a more dispersed state. In iuid processes gases are used toconvey the catalyst and to keep it, during reactions, in the form of adense turbulent bed which has no definite upper interface between thedense (solid) phase and the suspended (gaseous) phase mixture ofcatalyst and gas. This type of processing requires .the catalyst to bein the form of a fine powder, generally in a size range of about 20 to200 microns. Other processes use catalysts in the form of beads of about1A; to 1/2 inch in diameter', or in the form of tablets or extrudedpellets.

The catalytic cracking system includes the cracking zone and aregeneration zone wherein carbon deposited on the catalyst is burned oliby exposing the catalyst to air at a temperature of about 900 to 1400 F.In the process of this invention, gas oil containing metal poisons and,if desired, heated to the vapor state, eg. to a temtoerature of about400 to 800 F., is fed to a reactor in combination with regeneratedcatalyst. The cracked products pass overhead to a fractionator whichseparates gasoline and lower boiling materials from cycle oil and I3bottom products which can be blended into fuel oils, further processed,or recycled to the cracking reactor. The fractionator overhead includesgas and gasoline which are passed through a condenser to severalseparatory stages for separating out iixed gases from the gasolinefraction. The gasoline fraction, for removal of oxygenated and sulfurouscompounds such as phenols and hydrogen suliide which are considereddeleterious, is scrubbed with a circulating stream of NaOH solution,generally at about l25 Baume to convert these materials to sodiumcompounds which are readily separable from the gasoline with the aqueouscaustic phase. The gasoline from caustic treating can be further retlnedor sen-t directly to blending with other components or" the linishedgasoline.

The aqueous caustic may be recycled through the gasoline scrubbing zoneuntil it substartially loses its activ .y for removing gum formers. Theresulting aqueous solution or suspension of phenolics and otherorgano-sodium materials is usually forbidden by law to be dumped intostreams, etc., and a treatment of these wastes is desirable toinsolubilize the organic materials and thereby provide for separation ofthe bulk of :the waste as more or less innocuous aqueous solution or"inorganic materials. Also, the organic materials may be saleable forcertain end uses.

Various techniques have been suggested to remove the metal contaminantsfrom synthetic gel cracking catalysts. For example, the processes ofcopending applications, Serial Nos. 763,834, tiled September 29, 1958now abandoned; 849,199, tiled October 28, 1959; 842,618, tiled September28, 1959 now abandoned; and 19,313, iiled April 1, 1960 now abandoned,are illustrative of such processes and are incorporated herein byreference. A poisoned catalyst may be reduced in nickel content by anaqueous wash when nickel contaminants are put into a water-dispersibleform by treating a sulfided nickelcontaminated catalyst. Suliiding maybe performed as disclosed in copending application Serial No. 763,834,tiled September 29, 1958; or Serial No. 842,618, tiled September 28,1959. lt has been found that iron and vanadium may be removed from acatalyst by converting the metals into volatile compounds; achlorination treatment can convert iron and vanadium to volatilechlorides as reported in copending application Serial No. 849,199, filedOctober 28, 1959. Also as pointed out in copending application SerialNo. 19,313, tiled April 1, 1960, a preliminary treatment of the catalystwith molecular oxygencontaining gas is of value in increasing thequantity of vanadium removed.

This invention advantageously includes demetallization effected bychlorination of the metal contaminated catalyst. Chlorination may becombined with other procedures for improved demetallization of catalystswhich have become poisoned in the cracking process of the invention. Forexample, the chlorination may be preceded by sulding the poisoningmetals to improve'the removal of nickel poisons in subsequent steps; thetreatment with the chlorinating agent may be followed by treatment withan inert vapor to enhance volatilization of the iron and vanadiumchlorides formed. These iron and vanadium chlorides are essentiallyacidic in character and cannot be released to the atmosphere becausethey readily condense in the vicinity of the apparatus when the ellluentvapor cools. Also, the chlorinator ellluent may contain poisonous gasessuch as phosgene.

A conversion to vanadium chloride after the high temperature oxygentreatment preferably makes use of vapor phase chlorination at amoderately elevated temperature, up to Vabout 700 or even 1000 F.,wherein the catalyst composition and structure is not materially harmedby the treatment and a substantial amount ot the poisoning metalscontent is converted to chlorides. The conversion to chloride may beperformed after sulliding the poisoning metals, as described below. Thechlorination takes place at a temperature of at least about 300 F.,preferably about 550 to 656 F. with optimum results usually beingobtained near 600 F. The chlorinating agent is essentially anhydrous,that is, ir" changed to the liquid state no separate aqueous phase wouldbe observed in the reagent.

The chlorinating reagent is a vapor which contains chlorino or sometimesHC1, preferably in combination with carbon or sulfur. Such reagentsinclude molecular chlorine but preferably are mixtures of chlorinewith,-for example, a chlorine substituted light hydrocarbon, such ascarbon tetrachloride, which may be used as such or formed in-situ by theuse of, for example, a Vaporous mixture of chlorine gas with lowmolecular weight hydrocarbons such as methane, n-pentane, etc.

The stoichiometric amount of chlorine required to coniron, nickel andvanadium to their most highly chlori- :d compounds is the minnnum amountof chlorine ordinarily used and may be derived from free chlorine,

combined chlorine or the mixture of chlorine with a chlorine compoundpromoter described above. However, ie stoichiometric amount of chlorinefrequently is in a neighborhood ol only 0.001 g./g. of catalyst, a muchlarger amount of. chlorine, say about 1-40 percent active chlorinatingagent based on the Weight of the catalyst is generally used. The amountof chlorinating agent required is increased il any significant amount ofwater is present on the catalyst so that substantially anhydrousconditions preerably are maintained as regards the catalyst as well asthe clilorinating agent. The promoter is generally used in the amount ofabout 1-5 or l() percent or more, preferably about 2-3 percent, based onthe weight of the catalyst for good metals removal; however, even ifless than this amount is used, a considerable improvement in metalsconversion is obtained over that which is possible at .the sametemperature using chlorine alone. The amount of promotor may varydepending upon the manipulative aspects of the chlorination step, forexample, a batch treatment may sometimes require more promoter than in acontinuous treatment for the same degree o eiiectiveuess and results.The chlorine and promoter may be supplied individually or as a mixtureto a poisoned catalyst. Such a mixture may contain about 0.1 to 50 partscmorine per part of promoter, preferably about 1-10 parts per part ofpromoter. A chlorinating gas comprising about 1-30 weight percentchlorine, based on the catalyst, together with one percent or more S2C12gives good results. Preferably, such a gas provides l-lO percent C12 andabout 1.5 percent S2Cl2, based on the catalyst. A saturated mixture ofCC14 and Cl2 or HC1 can be made by bubbling chlorine or hydrogenchloride gas at room temperature through a vessel containing CC14; sucha mixture generally contains about 1 part CCl4z5-1O parts C12 or HC1.

Conveniently, a `ressure of about 01G0 or more psig., preferably about0-15 p.s.i.g. may be maintained in chlorination. rl`he chlorination maketake about 5 to minutes, more usually about 2O to 60 minutes, butshorter or longer reaction periods may be possible or needed, forinstance, depending on the linear velocity of the vapors. Excesses ofthe chlorinating vapors as Well as other acid-acting materials will bepresent in the chlorinator ellluent. These vapors generally areforbidden to be released to the atmosphere or released to sewage systemsas liquids without further treatment to mitigate their pollutingeiiects. Treatment with the chlorinating vapor may not remove from thecatalyst all of the iron and vanadium chlorides formed. The chlorinationmay theretore be followed or interrupted by a purge of the catalyst withinert gas such as nitrogen or flue gas at a temperature sufficientlyhigh to vaporize the chlorides.

After chlorination nickel may be removed from the catalyst by a liquidaqueous wash. This aqueous medium, for best removal or" nickel isgenerally somewhat acidic, and this condition may be brought about, atleast initially, by the presence of an acid-acting salt or othermaterial entrained on the catalyst. The aqueous medium can containextraneous ingredients in trace amounts, so long as the medium isessentially Wa-ter and the extraneous ingredients do not interfere withdemetallization or adversely affect the properties of the catalyst.Ambient temperatures can be used in the Wash but temperatures of about150 F. to the boiling point of water are sometimes helpful. Pressuresabove atmospheric may be used but the results usually do not justify theadditional equipment. In order to avoid undue solution of alumina from achlorinated catalyst, contact time in this stage is preferably held toabout 3 to 5 minutes which is suiicient for nickel removal. However,contact periods as low as 1 minute have been satisfactory as Well aswashing for a period of about 2-5 hours or longer. r1`he Wash solutionalso provides another waste disposal problem. rl`he acidity of the WasteWash solution as Well as of the Waste chlorinator etiluent gas stemsprimarily from chlorine, ionizable chlorine compounds and materialswhich decompose to either of these, other materials in these mixturesbeing in general too weakly acidic to be signicant Waste disposalproblems. Also, since practically all of the chlorine and chlorinecompounds fed to the chlorinator reappear in either the Waste gas orwaste liquid, the acidity of the Wastes is determined by the chlorinefed to the chlorinator. Thus the agent used to neutralize these acidWastes should provide two moles of a univalent base for each mole ofmolecular chlorine, or equivalent amounts for ionizable chloridessupplied to the chlorinator.

As mentioned above, the poisoned catalyst may be sulided beforechlorination. The suiding step can be performed by contacting thepoisoned catalyst with elemental sulfur vapors, or more conveniently bycontacting the poisoned catalyst with a volatile suliide, such as H25,CS2 or a mercaptan. The contact with the sulfur-containing vapor can beperformed at an elevated temperature generally in the range of about 500to 1500 F., preferably about l800 to 1300" F. @ther treating conditionscan include a sulfur-containing vapor partial pressure of about 0.1 to30 atmospheres or more, preferably about 0.5-25 atmospheres. Hydrogensultide is the preferred sulding agent. Pressures below atmospheric canbe obtained either by using a partial vacuum or by diluting the vaporwith gas such as nitrogen or hydrogen. The -time of contact may vary onthe basis oi the temperature and pressure chosen and other factors suchas the amount of metal to be removed, The sulding may run for, say, upto about 20 hours or more depending on these conditions and the severityof the poisoning. Temperatures of about 900 to l200 F. and pressuresapproximating 1 atmosphere or less seem near optimum for suliiding andthis treatment often continues for at least 1 or 2 hours but the time,of course, can depend upon the manner of contacting the catalyst andsuiiding agent and the nature of the treating system, e.g. batch orcontinuous, as well as the rate of diiusion within the catalyst matrix.

The described demetallization procedures produce signiticantly greaterremoval of vanadium when, upon removal of the poisoned catalyst from theconversion systern, it is regenerated, given a treatment at elevatedtemperatures with molecular oxygen-containing gas, and Washed with theliquid aqueous solution before returning the catalyst to the hydrocarbonconversion system. Ordinarily, the catalysts are 'treated before thepoisoning metals have reached an undesirably high level, for instance,about 2%, generally no more than about 1% maximum, content of vanadium.Prior to oxygen treatment, subjecting the poisoned catalyst sample tomagnetic ux may be founde desirable to remove any tramp iron particleswhich may have become mixed with the catalyst.

Regeneration of a catalyst to remove carbon is a relatively quickprocedure in most commercial catalytic conversion operations. Porexample, in a typical fiuidized cracking unit, a portion of catalyst iscontinually being removed from the reactor and sent to the regeneratorfor contact with air at about 950 to 1200 F., more usually about 1000 to1150 F. Combustion of coke from the catalyst is rapid, and for reasonsof economy only enough air is used to supply the needed oxygen. Averageresidence time for a portion of catalyst in the regenerator may be onthe order of about six minutes and the oxygen content of the efiluentgases from the regen-crater is desirably less than about 1/2 When lateroxygen treatment is employed, the regeneration of any particular quantumof catalyst is generally regulated to give a carbon content of less thanabout 0.5%.

Treatment of the regenerated catalyst With molecular oxygen-containinggas is described in copending application Serial No. 19,313, led Aprill, 1960. rl`he temperature of this treatment is generally in the rangeof about 1000 to 1800" F. but below a temperature Where the catalystundergoes any substantial deleterious change in its physical or chemicalcharacteristics. lf any signicant amount of carbon is present in thecatalyst at the start of this high-temperature treatment, the essentialoxygen contact is that continued after carbon removal. ln any event,after carbon removal, the oxygen treatment of the essentiallycarbon-free catalyst is at least long enough to convert a substantialamount of vanadium to a higher valence state, as evidenced by asignificant increase, say at least about 10%, preferably at least about100%, in the vanadium removal in subsequent stages of the process. Thisincrease is over and above that Which Would have been obtained by theother metals removal steps without the oxygen treatment.

The treatment of the vanadium-poisoned catalyst with molecularoxygen-containing gas prior to sultidation and/or chlorination ispreferably performed at a temperature of about 1150 to 1350 or even ashigh as 1600 F. and at least about 50 F. higher than the regenerationtemperature. Little or no eiect on vanadium removal is accomplished bytreatment at temperatures signiiicantly below about 1000 F., even for anextended time. The upper temperature, to avoid undue catalyst damage,will usually not materially exceed about 1600 or 1800" F. The durationof the oxygen treatment and the amount of vanadium prepared by thetreatment for subsequent removal is dependent upon the temperature andthe characteristics of the equipment used. The length of the oxygentreatment may vary from the short time necessary to produce anobservable effect in the later treatment, say, a quarter or an hour to atime just long enough not to damage the catalyst. In a relatively staticapparatus such as a mutlie furnace, the effectiveness of the treatmentcan increase With the time over a rather extended period; in other typesof apparatus, however, such as a flow reactor, Where there is morethorough Contact of catalyst and gas, little increase in effectivenesswas observed after about four hours of treatment.

The oxygen-containing gas used in the treatment contains molecularoxygen as the essential active ingredient. rThe gas may be oxygen, or amixture of oxygen with inert gas, such as air or oxygen-enriched air andthere is little significant consumption of oxygen in the process. Thepartial pressure of oxygen in the treating gas may range Widely, forexample, from about 0.1 to 30 atmospheres, but usually the total gaspressure will not exceed about 25 atmospheres. As the oxygen partialpressure increases the time needed to increase the valence of a givenamount of vanadium in general decreases. The factors of time, partialpressure and extent of vanadium conversion may be chosen with a View tothe most economically feasible set of conditions. It is preferred tocontinue the oxygen treatment for at least about 15 or 30 minutes with agas containing at least about 1%, preferably at least about 10% oxygen.

In this invention the waste caustic from gasoline nishing is used todestroy poisonous materials such as phosgene and to neutralize thegaseous and aqueous acid-acting Y Wastes from demetallization. The spentcaustic may have a pil of about 7 to l2 when it is exhausted; catalystslurry wash Water may have a pH of about 2 to and the rinse water mayhave a pH of about 4 to 7. The effectiveness of the caustic however, isgre-ter than pH test methods indicate; the generally organic or otherslightly ionized anions with which sodium is combined in the spentcaustic will tend to precipitate from the solution when converted to theacid, freeing further sodium ions for reaction with waste inorganicstrong acid-acting materials. Thus, the waste caustic solution has aneilectiveness for neutralizing strong acid equivalent to its originalstrength before use in gasoline iinishing. The amount o caustic wastemixed with acid waste will vary depending on the conditions of theprocessing scheme. However, in general, as ientioned above, enough wastecaustic will be used to supply two moles of sodium for each mole ofchlorine gas employed in the dernetallization. The extent of causticaddition will be suicient to bring the aqueous wastes to a substantiallyneutral condition and the acid waste will in general be suiicient ltospring substantially all of the organic materials from the wastecaustic. The aqueous caustic decomposes plies-gene to HC1 and C02. lnthe practice of this invention it may sometimes be found that thecaustic wastes are insuilicient for complete neutralization of theacids. ln such a situation, additional caustic or other alkalinematerial may be added to the neutralization mixture. Alternatively, therate of caustic replacement in the gasoline tinishing can be increased.

rhe process i the invention will be better under tood by reference tothe accompanying schematic drawing which illustrates the process in anembodiment which uses uidized beds of catalyst. Catalyst conveying insuch procesing schemes is generally perf rmed by gravity and by airwhich is usually supplied by blowers, not shown in the drawing.

Gas oil containing metal poisons is vaporized and conducted into thesystem by conduit 1li, from an external source, not shown. At thejuncture l?. with the regenerator standpipe 14, gas oil vapors pick upregenerated catalyst and convey it through the conduit 1o Vto the iluidcracking reactor 13 where a signilicant amount of the gas oil isconverted to light hydrocarbon gases and materials boiling in thegasoline range. These essentially hydrocarbon products, with a smallamount or oxygen, sulfur, etc., containing materials leave the cracherthrough the effluent conduit 2@ after perhaps passing through a cycloneseparator 22 which disentrains catalyst lines from the product vapors.

The product is brought by conduit Ztl tothe fractionator 24 whichseparates the product mixture on the basis of the boiling points of theconstituents. The bottoms (nonvaporized) fraction is removed from thefractionator by the line 26, heavy cycle oil by the line 28 and lightcycle oil by the line 3i?. Each ot these fractions is capable of certainimmediate end uses, but they can be recycled singly or combined to thecraliing zone 1d.

The gasoline fraction, containing lower boiling materials, is conductedby line 32 to condenser 34 where, perhaps by indirect heat exchange withwater from a conduit 36, the greater part of the normally liquidfraction is condensed. The condenser efiluent may then pass by means ofline 35 to an accumulator ill Where the eluent is held in a quiescentstate to allow xed gases to disentrain themselves from the liquidfractions which are removed by line 42 to the absorber 44. ln theabsorber, gas from line 46 of accumulator di), condensed by compresso/r48 and conducted by line 5d, passes countercurrent to the liquidfraction to extract further dissolved gases from the liquid fraction.Substantially all the methane and ethane are thus removed from theliquid fraction by the line 52. The line d conveys the liquid fractionto the debutanizer 5d where the C4 materials are removed and carriedaway by line 58.

Gasoline is conveyed from debutanizer 56 by the line u to the scrubbingtower o2. An aqueous caustic solution is fed to the top or the scrubberby line 6ft, perhaps from the external source o5, where it passescountereurrently to the gasoline, removing oxygenated and/ orsulfurcontaining materials. Finished gasoline passes out of the scrubberby line 63 to use. The caustic is drawn from the bottom of the scrubberby line 7b whence it may be recycled through line 72 to line 64, or, ifexhausted, drawn oil byline 7e to storage in the tank 7o.

Catalyst from cracking reactor 18, contaminated with colte and nie-talpoisons, is drawn oil, more or less continuously, through the standpipe12d. At the juncture 122 the catalyst is niet by air -irom a souce 124which conveys the catalyst to regenerator lio by means of pipe Theair-catalyst mixture arrives, close to the combustion temperature ofcarbon, in the regenerator where such combustion tales place. Thiscombustion restores or maintains the activity of the catalyst byremoving carbon. lt will be understood that in this specication andclaims regeneration refers to this carbon burn-off procedure. In theprocess of this invention the regeneration conditions, including therate of withdrawal of catalyst from the cracker and residence ltime inthe regenerator, are generally controlled so that the carbon content ofthe catalyst leaving the regenerator is less than about 5.0%, preferablyless than about 0.5%. Waste gases from the regenerator leave by means ofline 129. The catalyst, reduced in carbon content, returns by means ofthe standpipe 1.4 to the cracker, as explained above.

The standpipe may be provided with the bleed conduit 13@ for withdrawingcatalyst to be demetallized. The catalyst may be conv-eyed todemetallization by air from the line 132. Ordinarily the fraction ofregenerated catalyst withdrawn in this slip-stream to demetallizationwill be regulated to keep catalyst metals poisons from reaching anundersirably high level, for instance, about 2% generally no more thanabout 0.5% maximum, content of one or. both nickel and vanadiumcalculated as their common oxides. Treatment is usually not warrantedunless the catalyst has at least about 25-50 ppm. of nickel oxide and/or about Z50-50G ppm. Vanadium pentoxide.

The derntallization comprises one or more procedures which may produceacid-acting waste materials. The amount of Ni, V or Fe removed inpracticing any particular procedure or the proportions of each which areremoved may be varied by proper choice of procedures and treatingconditions. When the catalyst is severely poisoned in relation to thetolerance of the reactor for poison, it may be necessary to repeat someor all of the treatment when batch operation are employed, or toincrease the dernetallization rate, that is, the proportion of catalystsent to demetallization, in a continuous process, to reduce the metalsto an acceptable level, perhaps with variations where one metal isgreatly in excess. The demetallization procedure illustrated mairesprovision for heating, sulliding, chlorinating, washing md iiltering thecatalyst before its return to the cracking system in a water slurry, butit is to be understood that this series of steps is illustrative andthat this invention may include other dernetallization procedures aswell as procedures wherein some of the illustrated steps are omitted.

In the embodiment of this invention shown in the drawing, the catalystpasses through conduit to an outer chamber 134 of the `suliider 13d. Thecatalyst particles and the sulfider itself are raised to the suliidingtemperature of say about 1150 F., advantageously by burning a fuel inthe bed of particles in this chamber. The tuel, with or without theaddition of combustion supporting gas, may be supplied by the line 138and the exhaust gas may be vented by the line 140. The heated catalystparticles may How into the suliiding chamber as through the opening 142.A suliiding gas, eg., H28 or CS2 is passed to the bottom of the suliider136 by the line 144. Exhaust zsulding gas is passed out of the sulder135 through the line 146. These gases may be passed directly through theline 14S to disposal or other use. Alternatively, sulder effluent may beconducted by line 146 to line 152 to a burner 154. This burner may besupplied with combustion supporting gas by line 156 and with a Vent 158leading to disposal or other use.

Sullided catalyst is removed from the sulder 136, preferably at thebottom, by line 160 to the chlorinator 162. The chlorinator is generallyan elongated chamber made of Monel or other chlorine resistant material4and may be provided with one or more internal grids 164, 166 for gasdistribution and break-up of catalyst particle agglomerates. Thechlorinating agent is brought to the chlorinator 162 from the conduit163. The agent may be preheated it desired and generally will comprise amixture of elemental chlorine with a promoter as described above. Excesschlorinating vapor is withdrawn from the chlorinator by the line 170 forconduction to the contact tower 172.

The chlorinated catalyst leaves the chlorinator 162 by the line 202 tothe slurry tank 204 which is advantageously provided with stirrer 206.In the slurry tank the chlorinated catalyst is admixed with a largevolume of water which may contain `acidifying agents with or withoutammonium ions, as described above. This very dilute slurry may beremoved from the tank 204 and brought through the line 208 to the filter210 which may advantageously be a rotary vacuum drum lter as shown, or apan filter. The cake of catalyst particles on the filter may be rinsedby Water from line 212, scraped from the lter by doctor blade 214 andfall through the path or conduit 216 into the reslurry tank 218 whichadvantageously is provided with a stirrer 220, from which the catalystmay be returned, for example, to the regenerator by the line 222 as aWater slurry. Alternatively, the route of catalyst back to theregenerator may be by means of drying and calcination zones to removefree and combined water from the catalyst. Wash waiter and rinse waterremoved from the catalyst slurry are conveyed from the filter by line224 to the line 226 for introduction into the neutralizing andseparating chamber 228.

Spent caustic is conveyed from storage tank 76 by line 230 to the upperportion of contact tower 172 which may be provided Wit-h solid inertcontact material for instance in a bed 232. in this tower, the aqueouswaste caustic solution contacts the acid-acting gaseous chlorinationeffluent from line 170. The aqueous solution decomposes some components,eg., phosgene, neutralizes the acid components of these gases and scrubsout such materials. The neutralization also tends to precipitateorganics from the aqueous phase. Inert` gases pass from tower 172through line 174. The liquid stream passes from the bottom 234 of tower172 through the line 236 and to the chamber 228 accompanied by aqueouswash and rinse fluids from lter 210.V In the neutralizing and settlingchamber 2255, the mixed fluids settle into an upper organic layercomprising phenolics, etc., which may be drawn ofi by line 23S forrecovery, if desired, or burning, and a lower aqueous layer comprisingmostly water and inorganic salts which may be sent to sewage, usuallywithout further treatment, by line 240. In some instances the organiclayer settles to the bottom of chamber 22S so that the organic materialis drawn off at line 240 and the aqueous solution through line 238.

Example A gas oil containing about 0.16 p.p.m. Ni, 1.3 p.p.m. Fe and0.93 ppm. V had an API gravity of about 23.4, a Ramsbottom carbon ofabout 0.477 weight percent, a viscosity of about 44.3 seconds SayboltUniversal at 210 F., and an initial boiling point above about 420 F. atatmospheric pressure, was preheated to about 660 F., and introduced into-a tiuid catalytic cracker mixed with a finely divided cracking catalystat a presure of about p.s.i.g. The catalyst introduced into the 4feedline was a 26.4% A1203, silica-alumina Nalcat contact cracking 10catalyst having ui-dizable particle size as hereinbefore described. Thefeed attained a temperature of about 911 F. in the reactor and had aspace velocity of about 5.2 pounds of oil per hour per pound ofcatalyst.

The cracked products Were introduced into a fractionator where theproducts were separated into a cycle oil fraction boiling above about400 F., a gas fraction (C3 minus) and a C4 to 430 F. end point gasolinewhich cornprised 61 weight percent of the cracker etliuent. The gasolinecontains about 0.16% oxygenated or sulfur-containing materials which areremoved by scrubbing with -a caustic soda solution of about B. Spentcaustic is passed to a contact tower.

A stream of catalyst was continually removed from the reactor and sentto a regenerator Where it was contacted with air at about 1050 F. toburn oit the carbon.

, The regenerated catalyst was then returned to the cracking reactor.The rate `of circulation of catalyst between reactor and regenerator andback to the reactor is about eight times the weight of gas oil chargedper hour to the reactor.

A minor por-tion, totaling about 15% each day, of fluid unit catalyst iscontinuously removed as a side stream from the regenerator ot thecracker Where its carbon content is reduced from about 1.1 Weightpercent to about 0.2 Weight percent and is sent to a demetallizationsystem. This catalyst side stream contains about 41 p.p.m. Ni, 505 ppm.V and 1200 ppm. Fe.

The poisoned catalyst is further regenerated in the catalyst heatingportion of the demetallizer, and carbon content reduced to 0.04 Weightpercent based on the catalyst. it is then fluidized with H28 gas at atemperature of about 1175o F. for an average reaction time of one hour.The catalyst is then purged with flue gas at a temperature of about 575F. and chlorinated in a chlorination zone with an equimolar mixture ofl2 and CCL, at about 600 F. The chlorinator eluent gas `hasapproximately the following composition.

Component: Weight Percent Nitrogen 1.7 Carbon dioxide 6.1 Chlorine 4.8

.Carbon tetrachloride 24.8 Hydrogen chloride 45.1 Phosgene 13.3 Sulfurdichloride 3.2 Vanadyl trichloride 0.5 Ferrie chloride 0.5

This chlorinator eifluent is passed to the contact tower where it issent counterourrent to sutiicient Waste caustic from gasoline nishing toprovide about two moles of sodium for each mole of chlorine gas used inthe chlori` nation. The tower eiiuent comprises a gas consisting mostlyof hydrogen sulde and some nitrogen and carbon dioxide. The contacttower bottoms are sent to a neutralization and settling tank.

After about 1 hour average hold-up time in the chlorinator, the catalystis removed and slurried with Water using 2.3 gallons of water per poundof catalyst. A pH of about 2.2 is irnparted to this slurry by chlorineentrained in the catalyst, and the slurry serves to remove nickelchloride. The catalyst, substantially reduced in iron, nickel andvanadium content, is filtered from the Wash slurry, dried at about 350F. and returned to the regenerator. The metals content of the catalystis reduced by the procedure of this invention from 505 to 395 parts permillion vanadium, from 41 to 17 parts per million nickel and from 1200to 1070 parts per million iron.

The aqueous acidic medium ltered from the slurry is sent to theneutralization and settling tank where it serves to further precipitateorganics from the Waste caustic. An organic layer containing phenolics,etc.,

from tne caustic and carbon tetrachloride from the chlorinator eliuentgases is removed from the bottom of this settling chamber. An aqueousphase, containing dissolved salts and solid precipitates including Fe,

Ni and V hydroxides is removed from the top of the chamber to waste.

It is claimed:

1. In a method wherein a hydrocarbon cracking catalyst is contaminatedduring the catalytic cracking of a hydrocarbon feedstock, heavier thangasoline and containing nickel and vanadium, in a cracking zone at anelevated temperature to produce gasoline, and nickel and vanadium aredeposited on the catalyst, and the gasoline fraction produced by thecracking is treated with caustic, the catalyst is cycled between thecracking zone and a regeneration zone to remove carbon by oxidation, anda portion of the catalyst is bled from the cracking system and subjectedto a treatment including contact with a chlorinatiug vapor to aid invanadium removal from the catalyst which contact produces an acid-actingeffluent; the improvement which comprises combining the acid-actingeiiluent from the catalyst treatment with an amount of wast caustic fromgasoline treating sufficient to neutralize the acid-acting eiiuent.

2. The method of claim 1 in which the catalyst treatment produces bothan acid-acting vanadium containing vapor and an acid actingnickel-containing liquid, both of which are combined with the saidcaustic.

3. The method of claim 1 in which the demetallization includes Contactof the catalyst with an aqueous acidic medium.

4. The method of claim 1 in which said caustic is sodium hydroxide.

5. The method of claim 2 in which said caustic is sodium hydroxide.

6. The method of claim 2 in which the chlorination is eifected bycontact with an anhydrous chlorinating mixture comprising a chlorinatingagent selected from a group consisting of HC1 and C12 and a promoterselected from the group consisting of chlorine containing compounds ofcarbon and sulfur.

7. The method of claim 2 in which the demetallization procedure includessuliidfation'.

8. In a method wherein a hydrocarbon cracking catalyst is contaminatedduring the catalytic cracking of a hydrocarbon feedstock, heavier thangasoline and containing nickel and vanadium poisons, in a cracking zoneat an elevated temperature to produce gasoline, and nickel and vanadiumare deposited on the catalyst, and the gasoline fraction produced by thecracking is treated with caustic, the catalyst is cycled between thecracking zone and a regeneration zone to remove carbon by oxidation anda portion of the catalyst is bled from the cracking system and subjectedto a treatment including contact with a chlorinating Vapor to aid invanadium removal and an aqueous wash which Contact produces aqueousacid-acting wastes; the improvement which comsane/a 12?, prisescombining the aqueous, acid-acting wastes from the catalyst treatmentwith an amount of waste caustic from gasoline treating, having a pH ofabout 7 to 12, sulicient to neutralize the acid-acting wastes.

v 9. The method of claim 8 in which the catalyst treatment procedureincludes suldation.

10. The method of claim 8 in which the catalyst treatment procedureincludes Contact of the catalyst with an aqueous acidic medium.

1l. The method of claim 8 in which the said caustic is sodium hydroxide.

12. In a method wherein a hydrocarbon cracking catalyst is contaminatedduring the catalytic cracking of a hydrocarbon feedstock, heavier thangasoline and containing nickel and vanadium poisons, in a cracking Zoneat an elevated temperature to produce gasoline,

and nickel and vanadium are deposited on the catalyst,

and the gasoline fraction produced by the cracking is treated with anaqueous sodium hydroxide solution which treatment produces waste caustichaving a pH of about 7 to 12, the catalyst is cycled between thecracking zone and a regeneration zone to remove carbon by oxidation, anda portion of the catalyst is bled from the cracking system andsubg'ected to a treatment which includes contacting substantiallycarbon-free catalyst with a molecular oxygen-containing gas at atemperature of about 115() to about 1600 F., suliiding the poisoningmetalcontaining component on the catalyst by contact with a suldingagent at a temperature of about 800 to 1500 F., chlorinating poisoningmetal-containing component on the catalyst by contact with anessentially anhydrous chlorinating agent at a temperature of about 300to 100G" F., removing poisoning metal chloride in Vapor form from thecatalyst, contacting the catalyst with a liquid, essentially aqueousmedium to remove soluble, metal chloride from the catalyst, whichtreatment produces aqueous, acid-acting wastes; the improvement whichcomprises combining said acid-acting wastes from the catalyst treatmentwith an amount of said Waste caustic from gasoline treating sutl'icientto neutralize the acid-acting wastes.

13. The method of claim 12 in which the suliidation is eiected bycont-act with H28, and the chlorination is eilected by contact with ananhydrous chlorinating mixture comprising a chlorinating agent selectedfrom the group consisting of HC1 and C12 and a promoter selected fromthe group consisting of chlorine-containing compounds of carbon andsulfur.

References Cited in the le of this patent UNITED STATES PATENTS1,765,424 Hazeman et al. June 24, 1930 2,414,736 Gray Jan. 21, 19472,481,253 Snyder Sept. 6, 1949 2,488,718 Forrester Nov. 22, 19492,494,556 Hornaday Jan. 17, 1950 2,575,258 Cornell et al Nov. 13, 19512,640,807 Rice lune 2, 1953 2,850,462 Planch Sept. 2, 1958

1. IN A METHOD WHEREIN A HYDROCARBON CRACKING CATALYST IS CONTAMINATEDDURING THE CATALYTIC CRACKING OF A HYDROCARBON FEEDSTOCK, HEAVIER THANGASOLINE AND CONTAINING NICKEL AND VANADIUM, IN A CRACKING ZONE AT ANELEVATED TEMPERATURE TO PRODUCE GASOLING, AND NICKEL AND VANADIUM AREDEPOSITED ON THE CATALYST, AND THE GASOLINE FRACTION PRODUCED BY THECRACKING IS TREATED WITH CAUSTIC,THE CATALYST IS CYCLED BETWEEN THECRACKING ZONE AND A REGENERATION ZONE TO REMOVE CARBON BY OXIDATION, ANDA PORTION OF THE CATALYST IS BLED FROM THE CRACKING SYSTEM AND SUBJECTEDTO A TREATMENT INCLUDING CONTACT WITH A CHLORINATING VAPOR TO AID IN